/**
 * 
 */
package groovy.servlet;

import groovy.lang.Binding;
import groovy.lang.Closure;
import groovy.util.GroovyScriptEngine;
import groovy.util.ResourceException;
import groovy.util.ScriptException;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.codehaus.groovy.runtime.GroovyCategorySupport;

/**
 * @author trungsi
 *
 */
public class GwcGroovyServlet extends AbstractHttpServlet {

	/**
     * The script engine executing the Groovy scripts for this servlet
     */
    private GroovyScriptEngine gse;

    /**
     * Initialize the GroovyServlet.
     *
     * @throws ServletException
     *  if this method encountered difficulties
     */
    public void init(ServletConfig config) throws ServletException {
        super.init(config);

        // Set up the scripting engine
        gse = createGroovyScriptEngine();

        servletContext.log("Groovy servlet initialized on " + gse + ".");
    }

	@Override
	public void service(HttpServletRequest request, HttpServletResponse response)
			throws IOException {
		// Get the script path from the request - include aware (GROOVY-815)
        final String scriptUri = getScriptUri(request);

        // Set it to HTML by default
        response.setContentType("text/html; charset="+encoding);

        // Set up the script context
        final Binding binding = new ServletBinding(request, response, servletContext);

        // Run the script
        try {
            Closure closure = new Closure(gse) {

                public Object call() {
                    try {
                        return ((GroovyScriptEngine) getDelegate()).run(scriptUri, binding);
                    } catch (ResourceException e) {
                        throw new RuntimeException(e);
                    } catch (ScriptException e) {
                        throw new RuntimeException(e);
                    }
                }

            };
            GroovyCategorySupport.use(ServletCategory.class, closure);
            /*
             * Set reponse code 200.
             */
            response.setStatus(HttpServletResponse.SC_OK);
        } catch (RuntimeException runtimeException) {
            StringBuffer error = new StringBuffer("GroovyServlet Error: ");
            error.append(" script: '");
            error.append(scriptUri);
            error.append("': ");
            Throwable e = runtimeException.getCause();
            /*
             * Null cause?!
             */
            if (e == null) {
                error.append(" Script processing failed.");
                error.append(runtimeException.getMessage());
                if (runtimeException.getStackTrace().length > 0)
                    error.append(runtimeException.getStackTrace()[0].toString());
                servletContext.log(error.toString());
                System.err.println(error.toString());
                runtimeException.printStackTrace(System.err);
                response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, error.toString());
                return;
            }
            /*
             * Resource not found.
             */
            if (e instanceof ResourceException) {
                error.append(" Script not found, sending 404.");
                servletContext.log(error.toString());
                System.err.println(error.toString());
                response.sendError(HttpServletResponse.SC_NOT_FOUND);
                return;
            }
            /*
             * Other internal error. Perhaps syntax?! 
             */
            servletContext.log("An error occurred processing the request", runtimeException);
            error.append(e.getMessage());
            if (e.getStackTrace().length > 0)
                error.append(e.getStackTrace()[0].toString());
            servletContext.log(e.toString());
            System.err.println(e.toString());
            runtimeException.printStackTrace(System.err);
            response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e.toString());
        } finally {
            /*
             * Finally, flush the response buffer.
             */
            response.flushBuffer();
            // servletContext.log("Flushed response buffer.");
        }
	}
	
	/**
     * Hook method to setup the GroovyScriptEngine to use.<br/>
     * Subclasses may override this method to provide a custom
     * engine.
     */ 
    protected GroovyScriptEngine createGroovyScriptEngine(){
        return new GroovyScriptEngine(this);
    }
}
